Spark-plug.



j C. G. HARVEY. sPAnK PLUG. APPLICATION FILED Inn. 1913.

Patented July 3, 1917. j

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Specification of Letters Patent.

Patented July 3, 191 '7.

Application filed Hay 27,1918. Serialiio. 770,819.

To all whom it may concern:

Be it known that I, CHARLES G. HARVEY, (who have declared my intention to become a citizen of the United States,) residing at Devils Lake, in the county of Ramsey and State of North Dakota, have invented new and useful Improvements in sparkrlsllugs, of which the following is a specification.

The invention relates to spark plugs for use in connection with electric ignition systems'for internal combustion engines and provides a plug of the breech type, whereby the plug proper with its electrode may be removed quickly from the body or shell without requiring the detachment of such body from the engine and which usually cannot be easily efl'ected.

The invention provides a spark plug embodying inner and outer shells, t e latter constituting the body and being screwed into the head of the cylinder and the inner shell carrying the plug and having detachable connection with the outer shell by means of a bayonet joint. 1

The invention consists of the novel features, details of construction and combination of parts, which hereinafter will be'more particularly set forth, illustrated in the accompanying drawing, and pointed out in the a pended claim.

Reiiarring to the drawing, forming a part of the specification,

' plu '5 Figure 1 is aperspective view of a spark, embodying the invention.

ig. 2 is a vertical central section.

Fig. 3 is a detail view of the inner shell.

Fig. 4 is a view of the plug proper.

'Fig. 5 is atop plan view of. the inner shell, showing the spanner in operative position.

Corresponding and like parts are referred to in the following description, and indicated in all the views of the drawing, by'the same reference characters.

The numeral 1 designates the body' or outer shell, which is provided at its upper end with a polygonal portion to receive a wrench or ot er tool by means of which suelT body or shell is screwed into or out from the head of the cylinder, the lower portion of such body 'or' shell being externally threaded to make screw'connection with the cylinder. The body 1 has its lower portion contracted and its lower end further reduced to receive the small .end of the plu 2. Lugs 3 project inward fromthe sides 0 the shell prising an upstanding flange in the upper edge of which are formed notches 6to receive the en aging ends of a spanner 7 by means of w ichthe inner shell is turned either to tighten or loosen the same. Bayonet slots 8 are formed in opposite sides of the body 4: and are adapted to receive the lugs: 3, such parts constituting bayonet Jo nts, whereby the inner shell is secured within the outer shell when the parts are assembled. The head 5 is adapted to overlap the upper end of the body or outer shell 1. An inner flange 9 is formed at the lower end of the'body 4 and engages a shoulder 10 of the plug 11, thereby limiting the inward movement of such plug. A sleeve 12 engages the shoulder 10 and makes connection withthe inner shell, thereby retaining the plug 11 in position. The sleeve 12 may be secured to the inner shell either frictionally or in any positive manner.

The plug 11 may be of porcelain or other insulating material commonly employed in devices of this nature and is formed with a central opening in which is fitted an electrode 13, said electrod projecting beyond PPPOSIl'B GlIdS of the plug. When the plug IS in position the lower end of the electrode 13, which is enlarged, is spaced slightly from the lower end of the body or shell 1 so as to provide a gap for the passage of the spark. The plug 11 being. secured within the inner shell the latter is adapted to be detachably connected with thevouter shell for body by means of the bayonet joints, the

lugs 3 passing through the vertical slots and thence into the inclined slots of the arts 8, the inner shell being made secure y turning the same to cause the lugs 3 to ride upon the inclined edges. of the bayonet slots in a manner well understood. When it is re uired to remove the plug the inner shell is turned bymeans of the spanner 7' to bring the lugs in register with the vertical slots when the inner shell, together with the plug, may be easily withdrawn from the body or outer shell.

From the fore oing description, taken in connection with t e accompanying drawing, the advantagesof the constructloii and of the method of operation will be readily apthe art to which parent to those skilled in and while I have the invention appertains,

, described the principle of operation of the invention, to ether with the device which I now consi or to be the best embodiment thereof, I desire to have it understood that the device shown is merely illustrative, and g by said outer shell, a removable inner Shell provided with ba onet slots for engagement with the lugs o the outer shell an outwardly projecting annular flange edge of the outer shell and a frictionall ena'ged lining for said inner shell, sai linmg forming a rear closed removable wall for the bayonet slots.

In testimony whereof I afliir my signa- 25 ture in presence of two witnesses.

CHARLES G. HARVEY. Witnesses:

. L. P. Dawson,

HENRY G. MIDDAUGH.

fhrmed on s said inner shell, and overlapping the upper 20 

